The alloy with nominal composition Ni-33Al-31Cr-2.9Mo-0.1Hf-0.05Ho （%） has been directionally solidified by liquid metal cooling （LMC） and conventional high rate solidification （HRS） processes. Investigations reveal that the directionally solidified alloys are composed of primary dendritic NiAl, NiAl/Cr（Mo） eutectic cell and Hf solid solution. Compared with the conventional high rate solidification process, the liquid metal cooling process can provide higher thermal gradient and higher cooling rate. Higher thermal gradient widens the composition range of coupled zone and reduces the volume fraction of primary dendritic NiAl. Higher cooling rate restrains the diffusion and results in the refinement of the microstructure and the expansion of total contents of the solid solution elements （except Si） in NiAI and Cr（Mo） phases. In addition, casting defects including freckles, misoriented primary dendritic NiAl grains and discontinuities of primary dendritic NiAl grains decrease or even disappear completely in the directionally solidified alloys processed by liquid metal cooling process.
修改评论